Effects of W6+ occupying Sc3+ on the structure, vibration, and thermal expansion properties of scandium tungstate* *Project supported by the National Science Foundation of China (Grant Nos. 11574276 and 11874328), the Key Scientific Research Project of Universities in Henan Province (Grant Nos. 20B140018, 20A510012, and 19A140019), Key Scientific and Technological Project of Henan Province (Grant Nos. 202102210110, 182102210451 and 192102210002).

Abstract

We experimentally investigate effects of W6+ occupying the sites of Sc3+ in the unit cell of Sc2W3O12 (Sc8W12O48) on the structure, vibration and thermal expansion. The composition and structure of the doped sample (Sc6W2)W12O48 ± δ (with two W6+ occupying two sites of Sc3+ in the unit cell of Sc8W12O48) are analyzed and identified by combining the x-ray photoelectron spectroscopy and the synchronous x-ray diffraction with first-principles calculations based on density functional theory. Results show that the crystal with even W6+ occupying even Sc3+ in the unit cell is stable and maintains the orthorhombic structure at room temperature. The structure of the doped sample is similar to that of Sc2W3O12, and with even W occupying even positions of Sc in the unit cell and constituting the WO6 octahedra. Raman analyses show that the doped sample possesses stronger W–O bonds and wider Raman linewidths than those of Sc2W3O12. The sample doped with W also exhibits intrinsic negative thermal expansion in the measured range of 150 K–650 K.